Curve conveyors constructed as chain scraper conveyors, capable of shifting in their longitudinal direction e.g. by being towed by a winning machine situated at the head and equipped with crawler tracks, are known in various constructional forms (DE-OS 37 27 272, DE-PS 32 41 129, DE-OS 33 39 404). Such self-moving curve conveyors are used e.g. in room and pillar retreating working or under similar conditions.
In curve chain scraper conveyors, the actual conveying line consists of a plurality of short conveyor segments (providing conveyor channel lengths or run sections) which are connected, leaving clearance adequate for curve formation, by means of screw bolts or other connecting elements in a tension-resistant but articulated manner. The length of the conveyor segments and the amount of axial freedom at the connection zones determine the curvability of the conveyor, i.e. the smallest possible curve radius of the conveyor. When travelling along a curved course, the channel joints open at the outer side of the curve. This involves increasing the central length of the conveyor line. This change in length must be permitted by the scraper chain, which for this reason is adjustable in its effective length and tension by means of a loading device. If the loading device used is e.g a hydraulic cylinder device associated with a turn-round drum for the scraper chain, this device must be constructed so that the cylinders can manage the excess pressure when curves are formed and the conveyor line is correspondingly altered in length. Moreover the conveyor segment butt ends are pressed against one another by the preloading of the scraper chain, at both sides when the course of the conveyor is straight, but only at the inner side of the curve in curved regions. The greater the preloading of the scraper chain, the greater the forces and restoring moments tending to return the conveying line to a straight course again.
When the conveyor is moved bodily in the longitudinal direction e.g. by crawler track running gear at its head end, or by a winch or the like, the entrainment of the conveying line is effected on the one hand by the friction of the conveyed material in the conveyor run and on the other hand in the form of thrust via the scraper chain band circulating about the return point or turn-round point at the rear machine frame. This means that when the curve conveyor is displaced during conveying work the scraper chain is additionally loaded by the high towing forces. These forces are also transmitted via any chain preloading device, so that the device has to be made substantially stronger. In the stationary state of the conveyor the preloading cylinder has then to be switched back to a lower pressure level, to avoid high wear caused by conveying with excessively strongly preloaded scraper chains.